A cell maintains a life phenomenon by performing several biological functions, such as gene expression, cell growth, cell cycle, metabolism, signal transduction, and the like, through various and complex protein-protein interactions. Accordingly, the understandings of intracellular protein-protein interactions and functions of the interactions have been the foundation of the understandings of the life phenomenon and are an essential part for developing new drugs and treating diseases.
A representative method of investigating protein-protein interactions in vitro is an affinity chromatography method.
In the case of protein affinity chromatography, it is difficult to purify a protein. In addition, since the interactions between proteins are confirmed only in vitro, it may result in false-positive results for proteins to be bound by an electrostatic interaction during passing the proteins, which are not interacted in the cell, through a column.
That is, in order to perform a quantitative measurement, a method of investigating the protein-protein interactions according to the conventional technologies analyzes the interactions in the isolation of proteins from other intracellular materials by purifying each of the proteins that exist in the cell for analyzing the protein-protein interactions. Accordingly, there is a limit to analyze the protein-protein interactions at the single molecular level in the actual intracellular environment with co-existing other proteins, and the like.
Moreover, a method of investigating the protein-protein interactions according to the conventional technologies has a problem that the degrees of effects of other proteins on specific protein-protein interactions cannot be analyzed when other proteins are involved with the interactions in the actual intracellular environment.
In addition, there was a conventional limit to compare and measure quantitatively specific activated protein concentrations in the cell of an experimental group and the cell of a control group.